A telescoping vacuum cleaner suction tube of this type is known from DE 39 29 399 A1. In this case, the bow spring engages into recesses of the actuating element with the ends that face one another. When the actuating element is depressed, the bow spring merely acts as a dimensionally stable pressure transmitting element, by means of which a snap-in element situated opposite of the actuating element needs to be disengaged from the snap-in depression of the inner tube. This snap-in element consists of a flattened region that lies diametrically opposite of the bow spring on the actuating element. In order to once again engage the snap-in element into a snap-in depression, the snap-in element is constantly subjected to the force of a prestressed leaf spring that persistently presses the snap-in element in the direction of the snap-in depressions on the surface of the inner tube. An interlocking device of this type always requires two springs, namely                a) a bow spring that serves as pressure transmitting element and does not exert a spring force as such,        b) and a leaf spring that has the tendency to constantly press the snap-in element into one of the snap-in depressions of the inner tube under a prestress.        
The bow spring has an annular cross-section and the snap-in depression has a cross-section in the shape of a graduated circle. When shock-like compressive forces are exerted upon the ends of the outer and/or inner tube, the snap-in element may slide upward and out of the snap-in depression on an oblique plane against the force of the leaf spring, wherein the snap-in element is disengaged and an undesirable telescopic adjustment takes place. The leaf spring that presses the snap-in element back into the snap-in depression not only increases the manufacturing and assembly expenditures, but also requires a sleeve-like handle around the outer and inner tubes in order to accommodate and simultaneously secure the leaf spring such that not only the assembly expenditure is increased, but also the manufacturing expenditure.